l. Field of the Invention
This invention relates to telephone switching and, more particularly, to a telecommunications system having local telephone switches capable of retrieving and deploying enhanced subscriber services from an Advanced Intelligent Network (AIN) using a call-setup protocol.
2. History of the Prior Art
Modern telecommunications systems offer subscribers a large number of enhanced subscriber services. These services may include the provision of an 800 Services Database, a Credit Card Verification Database, Geographic Call Routing, Incoming Call Routing, Multi-location Extension Dialing, Network Automatic Call Distribution, Flexible Call Routing, Flexible Carrier Selection, CLASS Calling Name Delivery Database, and others. Some telephone service providers are currently analyzing the use of a system known as the Advanced Intelligent Network (AIN) to provide these services.
FIG. 1 is a simplified block diagram of a typical telecommunications system 11 using an Advanced Intelligent Network (AIN) 12 to provide enhanced subscriber services. The AIN 12 and its associated Signaling System Number 7 (SS7) protocol are described in the industry standard, "TR-NWT-000246, Bell Communications Research Specification of Signaling System Number 7," which is hereby incorporated by reference. A large number of Local Switches (LSs) 13a-n may be connected to a Service Switching Point/Tandem (SSP/T) 14 via multi-frequency (MF) links 15. "tandem", as used herein, may be a local, LATA, or access tandem. The LSs 13a-n provide connections for subscribers 16a-n into the telecommunications system 11. The AIN 12 uses a system of high speed telecommunications links known as a Common Channel Signaling (CCS) network which employs the standard SS7 signaling protocol to link all of the components of the AIN 12. Standard telephony diagrams, and all figures herein, indicate links utilizing the SS7 signaling protocol as dotted lines and MF trunks as solid lines.
The components of the AIN 12 may include the SSP/T 14, one or more Signal Transfer Points (STPs) 18a-n which act as intermediate switching nodes, and one or more Service Control Points (SCPs) 19a-n. The SCPs 19 each contain a database of enhanced subscriber services which are accessed and controlled by a Service Logic Program (SLP). The SCP 19 currently utilizes a standardized protocol known as Transaction Capabilities Application Part (TCAP) for coordination of functions. The current version of the protocol required for communication with the SCP 19 is TCAP/AIN Release 0.1. The SCP 19 is described in the Bellcore standard, "TA-NWT-001280, Advanced Intelligent Network (AIN) Service Control Point (SCP) Generic Requirements," which is hereby incorporated by reference. The SCP 19 acts as a repository for enhanced subscriber services which may be accessed by any one of the LSs 13a-n. In the past, each LS had to be individually upgraded with enhanced subscriber services. With the implementation of the AIN 12, and the required communications capabilities in the LSs, new enhanced services need only be added to the SCP 19.
LSs 13 which have been upgraded to communicate utilizing the SS7 signaling protocol, and the latest release of the TCAP/AIN communications protocol, may communicate directly with an STP 18 and from there with an SCP 19 or other SSP/Ts, utilizing the high speed CCS network. LSs 13 which have not been upgraded with SS7 signaling capability, or with the TCAP/AIN communications protocol, must communicate over lower speed MF trunks 15 with the SSP/T 14 which, in turn, utilizes the SS7 signaling protocol, the TCAP/AIN communications protocol, and the CCS network to communicate with the STPs 18 and the SCPs 19. Dependence on MF trunks for access to the AIN 12 can substantially lengthen the time required to retrieve subscriber services, and ties up an expensive MF trunk which remains open and occupied during the retrieval period. The message flow utilized to retrieve an enhanced subscriber is described in more detail in conjunction with FIG. 4 below.
Another transaction often carried out utilizing the CCS network is call setup. Call-setup messages utilize a call-setup protocol known as the Integrated Services Digital Network (ISDN) User Part (ISUP) call-setup protocol. The ISUP call-setup protocol is described in the Bellcore standards, "TR-NWT-000317. Switching System Generic Requirements for Call Control Using the Integrated Services Digital Network User Part (ISDNUP)", "TR-NWT000394, Switching System Generic Requirements for Interexchange Carrier Interconnection Using the Integrated Services Digital Network User Part (ISDNUP)", and "TR-NWT000444, Switching System Requirements Supporting ISDN Access Using the ISDN User Part", which are hereby incorporated by reference.
FIG. 2 is a simplified block diagram illustrating a typical message flow utilized for call setup between two local telephone switches (LSs) 13 and 23 which have not been upgraded to utilize the ISUP call-setup protocol. Each non-I SUP LS is typically connected through a MF trunk 15 to an associated SSP/T. Thereafter, a series of ISUP messages is sent back and forth between an originating SSP/T 14, associated with a calling subscriber 16, and a destination SSP/T 24, associated with the called subscriber 21. The ISUP messages during call setup include an Initial Address Message (IAM) 22, an Address Complete Message (ACM) 25, an Answer Message (ANM) 26, a Release Message (REL) 27, and a Release Complete Message (RLC) 28. The ISUP messages are routed via the STP 18.
Many LSs in use today have been upgraded to utilize the ISUP call-setup protocol. FIG. 2a is a simplified block diagram illustrating a typical message flow utilized for call setup between two local telephone switches (LSs) 13 and 23 which have been upgraded to utilize the ISUP call-setup protocol. This upgrade allows ISUP-capable LSs to bypass the MF trunk link to the SSP/T, and communicate directly through the STP 18. Thus, the LS may perform call setup entirely over the CCS high speed telecommunications network. The CCS network is capable of transmitting at much higher data rates than multi-frequency (MF) trunks, and call setup can be completed over the CCS network much faster and more efficiently than in the past.
When utilizing the SS7 signaling protocol and the ISUP call-setup protocol for call setup, out-of-band signaling messages replace Multi -frequency (MF) and other in-band interoffice signaling mechanisms on selected circuits. The out-of-band messages are used to report circuit seizure and to transport address information, answer supervision, circuit release, etc. Thus, the network use of the SS7 signaling protocol for circuit-switched call connection and release differs fundamentally from traditional in-band circuit signaling. Instead of sending information on the facilities used for subscriber-to-subscriber communication, the switching system sends signaling information via a separate signaling network. The SS7 signaling protocol thereby allows switching systems to exchange information related to a circuit-switched connection even when the circuit is in the conversation mode.
FIG. 3 is a flow chart illustrating the typical manner in which a call is set up via the ISUP call-setup protocol, for both non-ISUP LSs and ISUP-capable LSs. At step 101, a calling subscriber 16 (FIGS. 2 and 2a) dials the telephone number of a distant subscriber 21. At step 102, if the LSs are not ISUP-capable, the call is routed over MF trunks to an originating SSP/T 14 at step 103. At step 104, ISUP call setup is invoked in the SSP/T 14 which then recognizes the dialed number as a number which requires ISUP routing, and seizes an ISUP trunk at 105. At 106, the originating SSP/T 14 then utilizes the ISUP call-setup protocol to send an Initial Address Message (IAM) 22, via the STP 18, to a destination SSP/T 24, asking for the status of the dialed subscriber's phone 21. At step 107, the destination SSP/T 24 queries the destination LS 23 about the status of the called subscriber's phone 21. The destination LS 23 determines the status of the called subscriber's phone 21, i.e., busy, idle, forwarded, out of service, etc. , at step 108, and returns this status to the destination SSP/T 24. At 109, the destination SSP/T 24 returns, via the STP 18, an Address Complete Message (ACM) 25 to the originating SSP/T 14, containing the status of the called subscriber's phone 21. The originating SSP/T 14 receives the ACM 25 and at step 110, the destination SSP/T 24 returns, via the STP 18, an Answer Message (ANM) 26 to the originating SSP/T 14 indicating that a MF trunk should be set up between the two SSP/Ts 14 and 24. At step 111, the MF trunk 15 between the originating SSP/T 14 and the destination SSP/T 24 is connected thereby providing speech capability between the calling subscriber 16 and the called subscriber 21. Once the call is terminated at step 112, a Release Message (REL) 27 is sent from the switch serving the first subscriber to hang up, to the switch serving the other subscriber. In response, a Release Complete Message (RLC) 28 i s returned.
If, however, at step 102 it was determined that the LSs are ISUP-capable, then the message flow moves to step 113 where ISUP call setup is invoked in the originating LS 13. The originating LS 13 recognizes the dialed number as a number which requires I SUP routing and seizes an ISUP trunk at 114, and at 115 sends an I AM 22 to the destination LS 23 via the STP 18 requesting the status of the dialed subscriber's phone 21. At 116, the destination LS 23 determines the status of the dialed subscriber's phone and returns an ACM 25 to the originating LS 13 containing the status. At step 117, the originating LS 13 returns an ANM 26 indicating that a MF trunk should be set up between the two SSP/Ts 14 and 24. At step 118, the MF trunk 15 between the originating SSP/T 14 and the destination SSP/T 24 is connected thereby providing speech capability between the calling subscriber 16 and the called subscriber 21. Once the call is terminated at step 119, a REL 27 is sent from the switch serving the first subscriber to hang up, to the switch serving the other subscriber. In response, a Release Complete Message (RLC) 28 i s returned.
FIG. 3a is a message flow diagram illustrating the flow of messages from a non-ISUP LS 13 to an ISUP-capable LS 23 during call setup and call release. At 201, the non-ISUP LS 13 seizes an MF trunk to the SSP/T 14. At 202, the SSP/T 14 sends an Initial Address Message (IAM) to the STP 18 which forwards it to the SSP/T 24 serving the called subscriber 21. At 204, the IAM is sent to the ISUP-capable LS 23 serving the called subscriber 21.
An Address Complete Message (ACM) is returned to the SSP/T 24 at 205. At 206, the ACM is sent to the STP 18 where it is forwarded to the SSP/T 14 at 207. An Answer message (ANM) is returned from the LS 23 to the SSP/T 24 at 208. At 209, the ANM is sent to the STP 18 where it is forwarded to the SSP/T 14 at 211. At 212, an answer signal is sent over the MF trunk to the non-I SUP LS 13.
Termination of the call is begun after the first subscriber hangs up (in this example, subscriber 16a). At 213, a release signal is sent over the MF trunk from the non-I SUP LS 13 to the SSP/T 14. A Release message (REL) is sent from the SSP/T 14 to the STP 18 at 214 which forwards the REL to the SSP/T 24 at 215. At 216, the REL is received by the LS 23 which returns a Release Complete Message (RLC) to the SSP/T 24 at 217. At 218, the SSP/T 24 sends the RLC to the STP which forwards the RLC to the SSP/T 14 at 219. At 221, a release complete signal over the MF trunk results in the disconnection of the call.
Referring again to FIG. 1, it can be seen that LSs 13a-n may access the AIN 12 either through MF trunks 15 and the SSP/T 14, or directly through SS7 links 17 to the STP 18. The message flows involved in determining the type of access, and in the method of service retrieval from the database in the SCPs 19, is shown in the flow diagram of FIG. 4. At step 121, a calling subscriber 16a (FIG. 1) dials the telephone number of a called subscriber 16n. At 122, it is determined whether or not the originating LS 13a has been upgraded to utilize the SS7 signaling protocol. If not, then the LS cannot directly access the AIN 12, and the signal is routed, at step 123, to the associated telephone Service Switching Point/Tandem (SSP/T) 14 via a low speed MF trunk 15. At step 124, AIN service is invoked in the SSP/T 14 which recognizes the dialed number as an AIN subscriber at 125. At step 126, the SSP/T 14 sends a Query message via the STP 18 to the SCP 19 requesting call processing instructions. The SCP performs a database lookup on the called subscriber's service that is being invoked at step 127, and then returns routing instructions to the SSP/T 14 at step 128. This response contains all of the information that is necessary to route the call (i.e., routing number, carrier, billing number, etc.). The SSP/T 14 receives the routing instructions from the SCP 19, and completes the call at step 129 by setting a MF trunk 15 between the calling subscriber 16a and the called subscriber 16n.
If, however, at step 122 it is determined that the LS is SS7-capable, then the message flow moves to step 131 where it is determined whether or not the LS has been upgraded with the latest release of the TCAP/AIN communications protocol. If not, then the flow again moves to step 123 where the signal is routed to the associated SSP/T 14 via MF trunk 15. Steps 124 through 129 are then utilized to retrieve the enhanced subscriber service.
If, at step 131, it is determined that the LS has been upgraded with the latest release of the TCAP/AIN communications protocol, then the LS may directly access the AIN 12. At step 132, AIN service is invoked in the LS which recognizes the dialed number as an AIN subscriber at 133. At step 134, the LS sends a Query message via the STP 18 to the SCP 19 requesting call processing instructions. The SCP performs a database lookup on the called subscriber's service that is being invoked at step 135, and then returns routing instructions to the LS 13 at step 136. This response contains all of the information that is necessary to route the call (i.e., routing number, carrier, billing number, etc.). The LS 13 receives the routing instructions from the SCP 19, and completes the call at step 137 by setting a MF trunk 15 between the calling subscriber 16a and the called subscriber 16n.
A major problem with the full implementation of enhanced subscriber services through the AIN 12 is the extremely high cost of the system to the service providers. The major factor in the expense of implementing an AIN is that each of the hundreds of LSs must be hardware/software upgraded to be able to communicate with the SCP 19 in order to access each of the stored subscriber services. The current interface requirements for the SCP 19 are described in the Bellcore standard, "TR-NWT001285 Advanced Intelligent Network (AIN) 0.1 Switch-Service Control Point (SCP) Application Protocol Interfaces Generic Requirements," which is hereby incorporated by reference. The upgrade to the LSs includes the implementation of the most recent version of the TCAP/AIN communications protocol (currently Release 0.1) in the LSs. Telephone service providers typically have hundreds of LSs, and although the cost for each provider will vary, each provider may, for example, be faced with an expense in excess of $500 million to upgrade its LSs to operate with the current release of the TCAP/AIN protocol.
Another problem is encountered by LSs which are SS7 and ISUP-capable, but are not AIN-capable and have not been upgraded to access a particular subscriber services such as 800 service, which currently requires its own communications protocol. As shown in FIG. 4, these LSs 13 (FIG. 1) must set up low data rate MF trunks to the SSP/T 14 in order to access the AIN and the SCP 19 which stores the 800 service. Thereafter, the SSP/T 14 communicates via the high speed CCS network and SS7 signaling protocol with the SCP 19 in order to retrieve the requested service. Modern industry regulations and service expectations are requiring LSs to provide enhanced services at faster connection times than are achievable with MF trunks.
It would be a distinct advantage to have a system which provides a database of enhanced subscriber services which may be accessed by LSs utilizing the high speed CCS network, but does not require the expensive upgrading of LSs to operate with the TCAP/AIN communications protocol. It would be another advantage to have a system which enables all LSs to connect directly into the AIN via the SS7 signaling protocol rather than using slower MF trunks through the SSP/T. The present invention provides such a system.